Efficient voltage conversion — buck, boost, flyback, and forward converters explained.
Switching Converter Basics
Unlike linear regulators that burn excess as heat, switching converters use energy storage elements (inductors, capacitors) and a switching element (MOSFET) controlled by PWM. The switch toggles at high frequency (50kHz-2MHz), storing and releasing energy. Efficiency is typically 85-95%. Higher frequency = smaller inductors/capacitors but more switching losses.
Buck Converter (Step-Down)
Vout = D × Vin, where D = duty cycle (0-1). When switch ON: inductor charges, current ramps up. When switch OFF: inductor discharges through diode to load. Output capacitor smooths the ripple. Key equation: ΔI_L = (Vin-Vout)×D×Ts / L. CCM (Continuous Conduction Mode): inductor current never reaches zero. DCM: current reaches zero — lighter loads, different dynamics.
Boost Converter (Step-Up)
Vout = Vin / (1-D). When switch ON: inductor stores energy (current ramps up). When switch OFF: inductor voltage adds to input — "boosting." Can generate high voltages from low sources (e.g., 3.7V → 12V). Used in LED backlights, battery-powered devices, and the "Joule Thief" circuit (boosts dying battery to light LED).
🎮 Interactive: Buck Converter
🎮 Interactive: Buck Converter
Adjust duty cycle and see how it controls output voltage with inductor current ripple.